Chapter Abstract: The revolving door phenomenon — when former public officials move to lobby jobs in the private sector, or vice versa — is an integral part of the EU lobbying picture. Revolving door rules, such as cooling-off periods or restrictions on contacts with former colleagues, are required to manage risks of conflicts of interest. Different actors in the EU institutions are covered by different such rules, including the EU Staff Regulations, the Code of Conduct for Commissioners and the Code of Conduct for Members of the European Parliament (MEPs), but these rules are often inadequate. A series of revolving door case studies illustrate both cases where the respective rules are too weak or ineffective. The European Ombudsman has been investigating the European Commission on its role in implementing stricter rules. Yet, public interest policy-making requires that the revolving door-type conflicts of interest to be monitored, regulated and publicly scrutinized.